1. Field of the Invention
The present invention relates to a device for manufacturing a composite yarn formed by the combination of a multiplicity of continuous glass filaments and of thermoplastic organic filaments.
More specifically, the invention relates to a device comprising at least one bushing fed with glass, from which is drawn a multiplicity of continuous glass filaments, and at least one extrusion head fed with a thermoplastic organic substance, from which is also drawn a multiplicity of continuous organic filaments. These organic filaments are drawn and projected by means of a venturi device into the sheet of glass filaments being drawn, all the said filaments then being gathered into the form of a composite yarn.
2. Discussion of the Background
Such an installation is described, for example, in Patent Application FR-A-2,698,038.
In the context of the invention described in that application, the thermoplastic filaments are drawn, separately from the glass filaments, by means of drums whose speed of rotation is controlled so as to give the sheet of thermoplastic filaments a speed greater than the drawing speed of the glass filaments. The sheet of thermoplastic filaments, optionally guided, passes through a venturi device which orients and projects the said sheet into the sheet of glass filaments being drawn. The device, which maintains the speed given to the thermoplastic filaments by the drawing drums, only projects the said filaments into the sheet of glass filaments, keeping them individualized. The difference thus created between the drawing speeds of the two categories of filaments has the effect of compensating for the shrinkage of the thermoplastic filaments which occurs before the composite yarn is wound. It is thus possible to obtain bobbins of composite yarn in which all the filaments of which it is composed have the same length. The appearance of a discrepancy between the desired speeds for the filaments, even when it is small, can result in a defect in the product obtained or can result in an incorrect operation of the installation.
This is the case when a discrepancy occurs between the speed given to the thermoplastic filaments by the drawing drums and the speed of the said filaments when they come into contact with the glass filaments.